1. Field of the Invention
The present disclosure relates to digital video signal processing, and more particularly, to methods and apparatus for processing digital color video signals generated by solid-state image sensing devices.
2. Description of the Related Art
FIG. 1 is a block diagram of a conventional solid-state image sensing device 100. Referring to FIG. 1, the solid-state image sensing device 100 includes an active pixel sensor (APS) array 110, a row driver 120 and an analog-to-digital converter 130. In addition, the solid-state image sensing device 100 further includes a controller (not shown) generating timing control signals for controlling the row driver 110 and the analog-to-digital converter 130 and addressing signals for selecting pixels of the APS array 110 and outputting a video signal sensed by the APS array 110. In a color solid-state image sensing device, generally, a color filter is located on each pixel of the APS array 110 to receive only a specific color light, as shown in FIG. 2. Here, at least three kinds of color filters are arranged in order to construct color signals. The most general color filter array has Bayer pattern in which red and green color patterns are repeatedly arranged in one row and green and blue color patterns are repeatedly arranged in another row. In this case, green is closely related to a luminance signal and is arranged in all rows, and red and blue are alternately arranged in rows to improve luminance resolution. In cellular telephones, digital still cameras and the like, a CMOS image sensor/charge-coupled device (CIS/CCD) having more than a million pixels arranged as the APS array 110 is used.
In the solid-state image sensing device 110 having the Bayer pattern pixel structure, the APS array 110 senses light using photodiodes and converts the sensed light into electric signals to generate video signals. The video signals output from the APS array 110 include red, green and blue analog signals. The analog-to-digital converter 130 receives the analog video signals output from the APS array 110 and converts them into digital video signals.
FIG. 3 is a block diagram of a conventional video signal processing system 300. Referring to FIG. 3, the video signal processing system 300 includes a solid-state image sensing device 310, a video signal processor 320 and a display 330. A red-green-blue (RGB) digital video signal output from the solid-state image sensing device 310 is processed by the video signal processor 320 and then output to the display 330 such as a liquid crystal display (LCD). When an image is displayed based on pixel data generated by the solid-state image sensing device 310, the image has lots of distortion and poor visual quality. Thus, the video signal processor 320 interpolates the pixel data generated by the solid-state image sensing device 310 with a predetermined scheme and outputs the interpolated pixel data to the display 330 to enhance the visual quality.
However, distortion of the output signal of the Bayer APS array applied to a video signal processing system such as a cellular telephone and a digital still camera has not been sufficiently corrected. Distortion requiring correction includes aliasing at edges, color moiré, loss of detail/blurring occurrence, false/pseudo color occurrence, and the like. These distortion phenomena can be generated because high-frequency areas such as lines or edges are not appropriately interpolated during the process of replacing bad pixels with interpolated data. Particularly, the bad pixels may produce white or black spots.